The invention relates to an oil mist separator of an internal combustion engine, comprising at least one gas-permeable diffusion separation body, through which a crankcase ventilation gas of the internal combustion engine can flow and in which oil mist present in the crankcase ventilation gas can be separated from the gas.
DE 197 29 439 A1 shows a closed crankcase ventilation system of an engine which must rely on the low-pressure support of a turbo charger inlet to take in leakage gases from the crankcase. The ventilation system includes a coalescer filter which filters the oil particles entrained by leakage gases before they enter into the turbo charger inlet. A relief valve prevents the crankcase from being put under excessive pressure as a result of a counter-pressure caused by either a clogged coalescer filter or by a malfunction of the engine. A low-pressure limiting valve prevents the low pressure support generated by the air inlet in the turbocharger from generating an absolute pressure which is too low. This prevents a pressure imbalance over the seals of the turbocharger. A bypass valve also prevents the crankcase from being set under excessively high pressure, by making the flow of leakage gases pass around the coalescer filter if the pressure in the crankcase becomes too high.
This known crankcase ventilation system evidently requires high technical expenditures because it comprises, in addition to the coalescer filter, two valves which significantly increase the manufacturing expenditures. Another disadvantage with this known ventilation system is seen in the fact that—in a clogged condition of the coalescer filter in which the bypass valve is opened—the leakage gases are no longer cleaned or only to a minor degree from the entrained oil particles or are even discharged uncleaned into the environment.
DE 600 23 217 T2 shows a gas/liquid inertia separator for the removal and fusion of liquid particles from a gas/liquid flow. This separator comprises a housing with an inlet to accept the gas/liquid flow and an outlet to discharge a gas flow. Furthermore, the separator comprises an inertia collector in the housing, comprising a collector surface in the path of the gas/liquid flow and causing a sharp change in direction of the same. The outlet accepts the gas flow after the sharp change in direction. The housing comprises an axial flow path through it, including a first flow path section for the gas/liquid flow between the inlet and a space on the collector surface, and a second flow path section for the gas flow between the space and the outlet. Furthermore, a flow-through filter is provided in the second flow path section which makes a safety filter available which traps gas particles entrained by the gas flow after separation on the inertia collector. The flow path presents precisely two 90° directional changes before entry into the flow-through filter, with a first directional change being arranged in the space at the collector surface and a second directional change in one of the first and second flow path sections, and with the gas flow after the two directional changes flowing axially through the flow-through filter to the outlet. In the housing, a nozzle structure is provided which presents a plurality of nozzles which take up the gas/liquid flow from the inlet and accelerate the gas/liquid flow through the nozzles against the collector surface. The collector surface and the nozzles are sufficiently spaced apart from each other by a space to prevent excessive resistance. The collector surface is a rough, porous collector surface which effects a separation of liquid particles from the gas/liquid flow with a smaller particle size than with a smooth, non-porous impingement surface, and this without the precise limit size for the particle separation of the latter and the collection of liquid particles in the porous collector surface.
Briefly stated, this separator is thus a series connection of an impingement separator and a flow-through filter, with the gas/liquid flow first running through the impingement separator and thereafter through the flow-through filter. Although in the operation of this separator, the largest portion of the oil particles is separated in the impingement separator, a certain portion of oil particles still continues to get into the flow-through filter, however; and consequently, in the course of the separator's operating time, the flow resistance of the flow-through filter increases due to the deposits permanently remaining therein until the flow-through filter is finally completely clogged. In this condition, the separator can no longer function at all, and malfunctions of the appropriate engine occur, unless the flow-through filter is cleaned or replaced in good time within the scope of maintenance measures.
DE 10 2005 043 198 A1 shows a gas/liquid inertia separator for the removal of liquid particles from a gas/liquid flow, with a housing comprising an inlet to accept the gas/liquid flow and an outlet to discharge the gas flow. Moreover, in the housing, the separator has a nozzle structure comprising one or a plurality of nozzle(s) with one or a plurality of opening(s) for accepting the gas/liquid flow from the inlet and for accelerating the gas/liquid flow through it, with one or a plurality of opening(s) of the nozzles providing a total flow through it. The separator further comprises an inertia impingement collector in the housing in the path of the accelerated gas/liquid flow, with the inertia impingement collector causing the separation of the liquid particles from the gas/liquid flow. Moreover, an actuator for a flow change is provided by means of which the total flow through the openings can be changed, preferable as a function of a preset parameter.
It is considered detrimental for this known separator that it comprises with the actuator a mobile, specifically resettable element which is subject to wear and tear in the operation of the separator and which renders the manufacture of the separator elaborate or expensive. Moreover, with moving parts in an oil mist separator, there is always the risk of a functional disorder of moving parts due to the fact that the oil particles and other components entrained in the crankcase ventilation gas have a sticky consistency which aggravates or finally entirely prevents the mobility of the actuator and the parts connected therewith the separator's increasing operating time.
From DE 10 2006 056 789 A1, an inertia impingement device is known which uses a gas flow rate to separate oil particles in the emissions of a crankcase in an internal combustion engine. A housing is here provided having a top side, a bottom side and sidewalls which essentially extend without interruption in between to determine a hollow body which has an inside chamber with an inner surface and an outside room with an outer surface. The top side comprises an opening to enable a flow nozzle extending through it, the nozzle having a diameter W and a constriction which extends over a predetermined distance T and stops at a predetermined distance S across from the bottom side. The nozzle is in fluid connection with the gas flow from the crankcase of the internal combustion engine. The bottom side is arranged in close vicinity to a heat source to serve as a primary impingement device plate. Furthermore, the side walls are provided with secondary impingement device plates which are located at predetermined places along the inner surface and extend into the inside chamber. Finally, a side wall with an opening is provided to enable a gas flow from the crankcase of the internal combustion engine through the housing over the primary impingement device plate, over the secondary impingement device plates and out of the opening in the sidewall to a turbo charger.
This device is a plain impingement separator providing good efficiency for/relatively large oil particles which the crankcase ventilation gas contains. Especially in modern internal combustion engines, however, a finer oil mist consisting of small oil particles increasingly occurs which can be separated only at a reduced efficiency in a plain impingement separator primarily by means of mass inertia forces. This results in an incomplete de-oiling of the crankcase ventilation gas and in a penetration of oil parts through the separator which may result in failures in the internal combustion engine, for example, because components—such as throttle linkages or air flow meters—which are located in an intake tract of the internal combustion engine are oil-contaminated, said tract taking up the gases from the separator. Moreover, the choice of arrangement of this separator is limited such that it must be arranged at a hot place, thus close to parts of the appropriate internal combustion engine which are hot in operation.